Polishing composition

Abstract

Provided is a polishing composition with which protuberance eliminating capability at the edge of a laser marking can be improved while maintaining polishing rate. Provided is a polishing composition for preliminary polishing of a silicon wafer having a laser marking. The polishing composition contains abrasive grains, a basic compound, a water-soluble polymer, and an anionic surfactant.

Description

polishing composition

[0001] The present invention relates to a polishing composition, and more particularly to a polishing composition for pre-polishing laser-marked silicon wafers. This application claims priority to Japanese Patent Application No. 2024-034280, filed March 6, 2024, the entire contents of which are incorporated herein by reference.

[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 process and a polishing process. The polishing process includes, for example, a preliminary polishing process (preliminary polishing process) and a final polishing process (final polishing process). The preliminary polishing process includes, for example, a rough polishing process (primary polishing process) and an intermediate polishing process (secondary polishing process). Technical documents related to polishing compositions used in the polishing process include, for example, Patent Documents 1 and 2.

[0003] Japanese Patent Application Publication No. 2020-035870 International Publication No. 2019 / 124442

[0004] For purposes such as identification, marks such as barcodes, numbers, and symbols (laser marks; hereinafter sometimes referred to as "LM") are sometimes applied to silicon wafers by irradiating the front or back surface of the silicon wafer with laser light. The application of LM is generally performed after the lapping process of the silicon wafer is completed and before the polishing process is initiated. Typically, the irradiation of laser light for applying LM creates an altered layer on the surface of the silicon wafer around the LM. Although the LM 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 after the LM application, it may become bulged, resulting in a decrease in yield. However, the altered layer is altered by the energy of the laser light, making it difficult to polish. Therefore, there is a need for a silicon wafer polishing composition that can flatten the bulge around the LM (hereinafter simply referred to as "bulge") (e.g., Patent Documents 1 and 2).

[0005] The present invention has been made in view of the above points, and an object of the present invention is to provide a polishing composition that can improve the ability to eliminate the protrusions around the LM while maintaining the polishing rate.

[0006] According to the present specification, there is provided a polishing composition for pre-polishing a silicon wafer bearing a laser mark (LM). The polishing composition comprises abrasive grains, a basic compound, a water-soluble polymer, and an anionic surfactant. By further adding a water-soluble polymer and an anionic surfactant to the polishing composition containing abrasive grains and a basic compound, it is possible to improve the elimination of protrusions around the LM while maintaining the removal rate.

[0007] In this specification, "eliminating the protrusion around the LM" means reducing the height from the reference surface (reference plane) around the LM of the substrate to be polished (i.e., a silicon wafer with an LM attached) to the highest point of the protrusion. The height from the reference surface around the LM of the substrate to the highest point of the protrusion can be measured, for example, by the method described in the examples below.

[0008] In some embodiments, the polishing composition has a water-soluble polymer content C Ｐ The content C of the anionic surfactant relative to Ｓ Weight ratio (C Ｓ / C Ｐ In the case where a water-soluble polymer and an anionic surfactant are used in combination, it is preferable that the ratio (C Ｓ / C Ｐ ) to 1 or less, the decrease in the polishing rate can be easily suppressed.

[0009] In some embodiments, the polishing composition preferably contains a nonionic water-soluble polymer as the water-soluble polymer. The effect of using a combination of a water-soluble polymer and an anionic surfactant can be more suitably exhibited in a configuration in which the water-soluble polymer is a nonionic water-soluble polymer.

[0010] In some embodiments, the polishing composition preferably contains a polymer containing a nitrogen atom (hereinafter also referred to as a nitrogen atom-containing polymer) as the water-soluble polymer. The effect of using a water-soluble polymer in combination with an anionic surfactant can be more suitably exhibited in a configuration containing a nitrogen atom-containing polymer as the water-soluble polymer.

[0011] In some embodiments, the polishing composition contains a water-soluble polymer having a weight average molecular weight (Mw) of 80×10 ４ It is preferable to contain the following water-soluble polymer: It is advantageous for the Mw of the water-soluble polymer not to be too high in order to better exert the effect of combination with an anionic surfactant.

[0012] In some embodiments, the polishing composition contains silica particles as the abrasive grains. In pre-polishing of silicon using silica particles as the abrasive grains, the protrusion of the LM periphery can be effectively eliminated while maintaining the required removal rate for the pre-polishing.

[0013] In some embodiments, the polishing composition further comprises a chelating agent. A polishing composition containing a chelating agent can suppress metal contamination of the polished surface after pre-polishing.

[0014] In some embodiments, the polishing composition can be a concentrate. The polishing composition disclosed herein can be manufactured, distributed, and stored as a concentrate.

[0015] This specification also provides a polishing method comprising pre-polishing a laser-marked silicon wafer with any of the polishing compositions disclosed herein. This polishing method can improve the elimination of protrusions around the LM while maintaining the required removal rate in pre-polishing.

[0016] 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.

[0017] <Abrasive Grains> 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; 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, polyacrylonitrile particles, and the like. Here, (meth)acrylic acid refers collectively to acrylic acid and methacrylic acid. The abrasive grains can be used alone or in combination of two or more types.

[0018] The abrasive grains are preferably inorganic particles, and in particular, particles made of metal or semi-metal oxides are preferred. Silica particles are a suitable example of abrasive grains that can be used in the technology disclosed herein. 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.

[0019] The type of silica particles is not particularly limited and can be selected as appropriate. Silica particles may be used alone or in combination of two or more types. Examples of silica particles include colloidal silica, fumed silica, precipitated silica, etc. Colloidal silica is particularly preferred because it is less likely to scratch the surface of the object to be polished and can exhibit good polishing performance (such as the ability to reduce surface roughness). The type of colloidal silica is not particularly limited and can be selected as appropriate. Colloidal silica may be used alone or in combination of two or more types. Suitable examples of colloidal silica include colloidal silica prepared by ion exchange using water glass (sodium silicate) as a raw material and alkoxide-processed colloidal silica. Here, alkoxide-processed colloidal silica is colloidal silica produced by the hydrolysis and condensation reaction of alkoxysilane.

[0020] 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 some preferred embodiments, at least a portion of the abrasive grains are contained in the polishing composition in the form of secondary particles.

[0021] The average primary particle diameter of the abrasive grains (e.g., silica particles) is not particularly limited, but from the viewpoint of maintaining the polishing rate while 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. In some embodiments, the average primary particle diameter may be, for example, greater than 40 nm, greater than 45 nm, or greater than 50 nm. Furthermore, from the viewpoint of preventing scratch generation, the average primary particle diameter of the abrasive grains is preferably 200 nm or less, more preferably 150 nm or less, even more preferably 120 nm or less, and particularly preferably 100 nm or less. In some embodiments, the average primary particle diameter may be 75 nm or less, or may be 60 nm or less.

[0022] In this specification, the average primary particle size of the abrasive grains 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 For example, in the case of silica particles, the average primary particle diameter (nm) = 2727 / BET value (m ２ The specific surface area can be measured using, for example, a surface area measuring device manufactured by Micromeritics, trade name "Flow Sorb II 2300".

[0023] The average secondary particle diameter of the abrasive grains 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 the ability to eliminate bumps, the average secondary particle diameter is preferably 30 nm or more, and more preferably 35 nm or more. In some embodiments, the average secondary particle diameter may be, for example, 40 nm or more, 45 nm or more, preferably 50 nm or more, and even 60 nm or more, or even 65 nm or more (e.g., 70 nm or more). Furthermore, from the viewpoint of preventing the occurrence of scratches, 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 embodiments, the average secondary particle diameter may be 120 nm or less, or 110 nm or less.

[0024] In this specification, the average secondary particle size of the abrasive grains refers to the particle size measured by dynamic light scattering, for example, using an Otsuka Electronics FPAR-1000 or an equivalent.

[0025] 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., the shape of a peanut shell), cocoon-shaped, confetti-shaped, and rugby ball-shaped.

[0026] The average aspect ratio of the abrasive grains is not particularly limited. In principle, the average aspect ratio of the abrasive grains is 1.0 or more, and can be 1.05 or more, 1.10 or more, or even 1.15 or more. Increasing the average aspect ratio tends to improve the polishing rate. In some embodiments, the average aspect ratio of the abrasive grains is greater than 1.2 (specifically, greater than 1.20), for example, 1.22 or more. Abrasive grains having an average aspect ratio greater than 1.2 are typical examples of the non-spherical abrasive grains. Furthermore, from the viewpoints of reducing scratches and improving polishing stability, 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.

[0027] The shape (outline) and average aspect ratio of the abrasive grains can be determined, for example, by electron microscope observation. 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.

[0028] The content of abrasive grains is not particularly limited and can be appropriately set according to the purpose. The content of abrasive grains relative to the total weight of the polishing composition may be, for example, 0.01 wt % or more, 0.05 wt % or more, or 0.1 wt % or more. With an increase in the content of abrasive grains, the polishing rate tends to improve, and the ability to eliminate bumps also tends to generally improve. In some embodiments, the content of abrasive grains may be 0.2 wt % or more, 0.5 wt % or more, 0.6 wt % or more, 0.8 wt % or more, 1.0 wt % or more, or 1.2 wt % or more. In addition, from the viewpoint of preventing scratches and saving the amount of abrasive grains used, in some embodiments, the content of abrasive grains may be, for example, 10 wt % or less, 5 wt % or less, 3 wt % or less, 2 wt % or less, 1.5 wt % or less, 1.2 wt % or less, or 1.0 wt % or less. These contents can be preferably applied to the contents in the polishing liquid (working slurry) supplied to the object to be polished, for example.

[0029] In the case of a polishing composition to be diluted before use in polishing (i.e., a concentrated solution), the content of abrasive grains is usually 50% by weight or less, and more preferably 40% by weight or less, from the viewpoints of storage stability, filterability, etc. In addition, from the viewpoint of utilizing the advantages of forming a concentrated solution, the content of abrasive grains is preferably 1% by weight or more, and more preferably 5% by weight or more.

[0030] <Basic Compound> 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 functions to chemically polish the surface to be polished, and can contribute to improving the polishing rate. The basic compound may be an organic basic compound or an inorganic basic compound. The basic compounds may be used alone or in combination of two or more.

[0031] Examples of organic basic compounds include quaternary ammonium salts such as tetraalkylammonium salts. The anion in the quaternary ammonium salts is OH. －For example, quaternary ammonium salts such as tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide can be preferably used. Among these, tetramethylammonium hydroxide (TMAH) is preferred.

[0032] Examples of inorganic basic compounds include ammonia; hydroxides of 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 lithium hydroxide, potassium hydroxide, sodium hydroxide, etc. Specific examples of the carbonates or hydrogen carbonates include ammonium hydrogen carbonate, ammonium carbonate, lithium hydrogen carbonate, lithium carbonate, potassium hydrogen carbonate, potassium carbonate, sodium hydrogen carbonate, sodium carbonate, etc.

[0033] Preferred basic compounds include ammonia, lithium hydroxide, potassium hydroxide, sodium hydroxide, tetramethylammonium hydroxide, tetraethylammonium hydroxide, ammonium bicarbonate, ammonium carbonate, lithium bicarbonate, lithium carbonate, potassium bicarbonate, potassium carbonate, sodium bicarbonate, and sodium carbonate. Among these, preferred examples include ammonia, lithium hydroxide, potassium hydroxide, sodium hydroxide, tetramethylammonium hydroxide, lithium carbonate, and potassium carbonate. Preferred basic compounds from the viewpoint of improving the ability to eliminate bumps include quaternary ammonium compounds (quaternary ammonium salts). Quaternary ammonium compounds may be used alone or in combination of two or more. Tetramethylammonium hydroxide is particularly preferred. Furthermore, from the viewpoint of improving the polishing rate, it is preferable to use carbonates such as potassium carbonate.

[0034] Although not particularly limited, from the viewpoint of achieving a good balance between maintaining the polishing rate and achieving surface flatness and eliminating protuberances, it is preferable to use a combination of quaternary ammoniums (e.g., tetramethylammonium hydroxide) and a carbonate (e.g., potassium carbonate) as the basic compound. Also, in some embodiments, in addition to the quaternary ammoniums (e.g., tetramethylammonium hydroxide) and / or the carbonate (e.g., potassium carbonate), an alkali metal or alkaline earth metal hydroxide (e.g., potassium hydroxide) is preferably used. In embodiments in which two or more selected from the quaternary ammoniums, the carbonates, and the hydroxides are used as the basic compound, the ratio of the components used is not particularly limited, and can be set to an appropriate range that achieves a good balance between maintaining the polishing rate and achieving surface flatness and eliminating protuberances, depending on the concentrations of other components contained, such as abrasive grains and water-soluble polymers.

[0035] The content of the basic compound relative to the total amount of the polishing composition is preferably 0.005 wt% or more, more preferably 0.01 wt% or more, even more preferably 0.05 wt% or more, from the viewpoints of polishing rate, surface flatness, and elimination of protuberances. It may be 0.07 wt% or more, or even 0.09 wt% or more. Increasing the content of the basic compound can also improve the dispersion stability of the polishing composition. The upper limit of the content of the basic compound is suitably 5 wt% or less. From the viewpoint of surface quality, etc., it is preferably 2 wt% or less, more preferably 1 wt% or less, even more preferably 0.5 wt% or less, and may be 0.4 wt% or less, 0.3 wt% or less, or 0.2 wt% or less (for example, less than 0.2 wt%). Note that 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, for example, to the content in the polishing liquid (working slurry) supplied to the polishing object.

[0036] In the case of a polishing composition to be diluted and used for polishing (i.e., a concentrate), the content of the basic compound is usually 10% by weight or less, and more preferably 5% by weight or less (e.g., 4% by weight or less), from the viewpoints of storage stability, filterability, etc. In addition, from the viewpoint of utilizing the advantages of forming a concentrate, the content of the basic compound is preferably 0.1% by weight or more, more preferably 0.5% by weight or more, and even more preferably 0.9% by weight or more (e.g., 1.5% by weight or more).

[0037] Abrasive grain content C in polishing composition Ａ Content of basic compounds C Ｃ Weight ratio (C Ｃ / C Ａ ) is not particularly limited as long as the effects of the technology disclosed herein are exhibited. Ｃ / C Ａ ) is suitably set to, for example, about 0.005 or more, and from the viewpoint of effectively exhibiting the effect of adding the basic compound, it is preferably 0.01 or more, more preferably 0.02 or more, and may be, for example, 0.05 or more. Furthermore, from the viewpoint of mechanical polishing by abrasive grains, dispersion stability of the composition, etc., the above ratio (C Ｃ / C Ａ ) is suitably, for example, approximately 1 or less, preferably 0.8 or less, more preferably 0.6 or less, and may be, for example, 0.5 or less, 0.4 or less, 0.3 or less, or 0.2 or less (e.g., less than 0.2).

[0038] <Water-soluble polymer> The polishing composition disclosed herein contains a water-soluble polymer. The water-soluble polymer can be useful for protecting the surface to be polished, improving wettability, etc. In addition, in the polishing composition disclosed herein, the water-soluble polymer can be used in combination with an anionic surfactant described below to effectively eliminate the protrusion of the LM periphery while maintaining the polishing rate. Any of nonionic, anionic, and cationic water-soluble polymers can be used as the water-soluble polymer.

[0039] Examples of water-soluble polymers include compounds 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, etc. in the molecule. The water-soluble polymer in the polishing composition disclosed herein may be, for example, a polymer containing a nitrogen atom, a polyvinyl alcohol-based polymer, a polymer containing an oxyalkylene unit, a carboxylic acid-based polymer, a cellulose derivative, a starch derivative, etc. One type of water-soluble polymer may be used alone, or two or more types may be used in combination.

[0040] (Nitrogen Atom-Containing Polymer) In some preferred embodiments, a nitrogen atom-containing polymer (typically a synthetic polymer) is used as the water-soluble polymer. A polishing composition containing a nitrogen atom-containing polymer is likely to produce a high-quality polished surface. Non-limiting examples of nitrogen atom-containing polymers include polymers having a nitrogen atom-containing ring; polymers containing N-vinyl type monomer units; polymers containing N-(meth)acryloyl type monomer units; and the like. One type of nitrogen atom-containing polymer may be used alone, or two or more types may be used in combination.

[0041] In some embodiments, an N-vinyl polymer can be used as the nitrogen atom-containing 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 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.

[0042] 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.

[0043] 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 (PVP), 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. From the viewpoint of achieving a good balance between maintaining the polishing rate and achieving surface flatness and elimination of protuberances, N-vinyl lactam polymers can be particularly preferably used as the water-soluble polymer disclosed herein.

[0044] In some embodiments, an N-(meth)acryloyl polymer may be preferably used as the nitrogen atom-containing polymer. The effects of the technology disclosed herein may be more preferably realized in a composition containing an N-(meth)acryloyl 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. Note that, in this specification, "(meth)acryloyl" refers collectively to both acryloyl and methacryloyl groups. Also, in this specification, "(meth)acryloyl group" refers collectively to both acryloyl and methacryloyl groups.

[0045] 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 N-n-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 a chain amide 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). In this specification, the term "(meth)acrylamide" refers to acrylamide and methacrylamide in a comprehensive sense.

[0046] 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 in which the copolymerization ratio of ACMO exceeds 50% by weight). In acryloylmorpholine-based polymers, the proportion of the number of moles of ACMO units in the number of moles of all 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.

[0047] (Polyvinyl Alcohol-Based Polymer) In some preferred embodiments, a polyvinyl alcohol-based polymer (typically a synthetic 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. One type of polyvinyl alcohol-based polymer may be used alone, or two or more types may be used in combination. 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.

[0048] The polyvinyl alcohol-based polymer may be unmodified polyvinyl alcohol (unmodified PVA) or modified polyvinyl alcohol (modified PVA). Here, unmodified PVA is a polymer produced by hydrolysis (saponification) of polyvinyl acetate, and has a repeating unit (-CH ２ -CH(OCOCH ３ )-) and a polyvinyl alcohol-based polymer that is substantially free of repeating units other than 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. In some embodiments, the degree of saponification of the unmodified PVA may be 98% or more (complete saponification).

[0049] The polyvinyl alcohol-based polymer may be a modified PVA containing VA units and non-VA units having at least one structure selected from oxyalkylene groups, carboxy groups, (di)carboxylic acid groups, (di)carboxylic acid ester groups, phenyl groups, naphthyl 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 from 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 from 3 to 7 carbon atoms may be a vinyl ester of a monocarboxylic acid having from 3 to 7 carbon atoms, such as vinyl propanoate, vinyl butanoate, vinyl pentanoate, or vinyl hexanoate. Suitable examples of the (di)acetone compound include diacetone (meth)acrylamide and acetylacetone.

[0050] In some preferred embodiments, an acetalized polyvinyl alcohol polymer is used as the polyvinyl alcohol polymer. An example of an acetalized polyvinyl alcohol polymer is a modified PVA in which a portion of the VA units contained in the polyvinyl alcohol polymer have been acetalized with an aldehyde. The modified PVA in which a portion of the VA units contained in the polyvinyl alcohol polymer have been acetalized with an aldehyde (acetalized PVA (ac-PVA)) can be obtained by reacting a portion of the hydroxy groups of the polyvinyl alcohol polymer with an aldehyde compound or a ketone compound to acetalize the polymer. Typically, the acetalized polyvinyl alcohol polymer is obtained by the acetalization reaction of a polyvinyl alcohol polymer with an aldehyde compound. In some preferred embodiments, the aldehyde compound has 1 to 7 carbon atoms, more preferably 2 to 7 carbon atoms.

[0051] Examples of the aldehyde compound include formaldehyde; linear or branched alkyl aldehydes such as acetaldehyde, propionaldehyde, n-butylaldehyde, isobutyraldehyde, t-butylaldehyde, and hexylaldehyde; and alicyclic or aromatic aldehydes such as cyclohexanecarbaldehyde and benzaldehyde. These may be used alone or in combination of two or more. With the exception of formaldehyde, one or more hydrogen atoms may be substituted with a halogen or the like. Among these, linear or branched alkyl aldehydes are preferred because of their high solubility in water and ease of acetalization reaction, and among these, acetaldehyde, n-propylaldehyde, n-butylaldehyde, and n-pentylaldehyde are more preferred.

[0052] In addition to the above, aldehyde compounds having 8 or more carbon atoms such as 2-ethylhexylaldehyde, nonylaldehyde, and decylaldehyde may also be used as the aldehyde compound.

[0053] Acetalized polyvinyl alcohol-based polymers have the following chemical formula: -CH ２The copolymer contains a VA unit, which is a structural moiety represented by —CH(OH)—; and an acetalized structural unit (hereinafter also referred to as a “VAC unit”) represented by the following general formula (1):

[0054] (In formula (1), R is a hydrogen atom or a linear or branched alkyl group, and the alkyl group may be substituted with a functional group.)

[0055] In some preferred embodiments, R in the above formula (1) is a hydrogen atom or a linear or branched alkyl group having 1 to 6 carbon atoms. R may be one of these groups or a combination of two or more of these groups. R is preferably a linear or branched alkyl group having 1 to 6 carbon atoms.

[0056] The acetalization degree of the acetalized polyvinyl alcohol-based polymer can be 1 mol% or more, may be 5 mol% or more, preferably 10 mol% or more, more preferably 15 mol% or more, even more preferably 20 mol% or more, particularly preferably 25 mol% or more (e.g., 27 mol% or more). From the viewpoint of improving hydrophilicity, the acetalization degree of the acetalized polyvinyl alcohol-based polymer is preferably less than 60 mol%, even more preferably 50 mol% or less, more preferably 40 mol% or less, particularly preferably 35 mol% or less (e.g., 33 mol% or less). In this specification, the "acetalization degree" refers to the proportion of acetalized structural units (VAC units) in all repeating units constituting the acetalized polyvinyl alcohol-based polymer.

[0057] Furthermore, as the polyvinyl alcohol-based polymer, a cation-modified polyvinyl alcohol into which a cationic group such as a quaternary ammonium structure has been introduced may be used. Examples of the cation-modified polyvinyl alcohol include those into which 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, has been introduced. Furthermore, as the vinyl alcohol-based polymer, a non-VA unit having the chemical formula: -CH ２ -CH(CR ５ (OR８ )-CR ６ (OR ９ )-R ７ )-, where R ５ ~R ７ each independently represents a hydrogen atom or an organic group, R ８ and R ９ are each independently a hydrogen atom or R １０ -CO- (wherein, R １０ represents an alkyl group. For example, R ５ ~R ７ When at least one of R is an organic group, the organic group may be a linear or branched alkyl group having 1 to 8 carbon atoms. １０ can be a straight or branched chain alkyl group having from 1 to 8 carbon atoms.

[0058] In some embodiments, the modified polyvinyl alcohol-based polymer is a modified polyvinyl alcohol-based polymer having a 1,2-diol structure in a side chain. ５ ~R ９ is a hydrogen atom (butenediol-vinyl alcohol copolymer (BVOH)).

[0059] 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.

[0060] 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, contained 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.

[0061] A polyvinyl alcohol-based polymer may contain multiple polymer chains with different VA unit contents within the same molecule. Here, the term "polymer chain" refers to a segment that constitutes a part of a single polymer molecule. For example, a polyvinyl alcohol-based polymer may contain, within the same molecule, a polymer chain A with a VA unit content of more than 50% by weight and a 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).

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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. Examples of N-vinyl monomers include monomers having a nitrogen-containing heterocycle (e.g., a lactam ring) and N-vinyl chain amides. Another example of the polymer chain B is a polymer chain having a repeating unit derived from an N-(meth)acryloyl monomer as the main repeating unit, i.e., an N-(meth)acryloyl polymer chain. Examples of N-(meth)acryloyl monomers include chain amides having an N-(meth)acryloyl group and cyclic amides having an N-(meth)acryloyl group. Another example of the polymer chain B is a polymer chain having an oxyalkylene unit as the main repeating unit, i.e., an oxyalkylene polymer chain. Examples of the oxyalkylene unit include an oxyethylene unit, an oxypropylene unit, an oxybutylene unit, etc. The oxyalkylene polymer chain may contain one type of oxyalkylene unit or two or more types of oxyalkylene units. For example, the oxyalkylene polymer chain may contain a combination of oxyethylene units and oxypropylene units. The oxyalkylene polymer chain containing two or more types of oxyalkylene units may be a random copolymer, a block copolymer, an alternating copolymer, or a graft copolymer of the corresponding alkylene oxides.

[0066] Further examples of the polymer chain B include polymer chains containing repeating units derived from alkyl vinyl ethers (e.g., vinyl ethers having an alkyl group having from 1 to 10 carbon atoms); polymer chains containing repeating units derived from monocarboxylic acid vinyl esters (e.g., vinyl esters of monocarboxylic acids having from 3 or more carbon atoms); polymer chains having as their main repeating units repeating units derived from vinyl dicarboxylates such as fumaric acid, maleic acid, and maleic anhydride; polymer chains having as their main repeating units repeating units derived from aromatic vinyl monomers such as styrene and vinylnaphthalene; and polymer chains into which cationic groups (e.g., cationic groups having a quaternary ammonium structure) have been introduced.

[0067] In this specification, unless otherwise specified, the term "main repeating unit" refers to a repeating unit contained in an amount of more than 50% by weight.

[0068] (Polymer Containing Oxyalkylene Units) In some embodiments, a polymer containing an oxyalkylene unit (typically a synthetic polymer) is used as the water-soluble polymer. Examples of polymers containing oxyalkylene units 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 type triblock copolymers and PPO-PEO-PPO type triblock copolymers. Typically, PEO-PPO-PEO type triblock copolymers are more preferred.

[0069] (Carboxylic Acid Polymer) In some embodiments, a carboxylic acid polymer is used as the water-soluble polymer. Examples of carboxylic acid polymers include polymers containing maleic acid units and polymers containing (meth)acrylic acid units. Examples of polymers containing maleic acid units include styrene-maleic acid copolymers or salts thereof, styrene-maleic anhydride copolymers, styrene sulfonic acid-maleic acid copolymers or salts thereof, copolymers of styrene sulfonate and maleic acid, and maleic acid-vinyl acetate copolymers. Examples of polymers containing (meth)acrylic acid units include polyacrylic acid or salts thereof, styrene-acrylic acid copolymers or salts thereof, styrene sulfonic acid-acrylic acid copolymers or salts thereof, copolymers of styrene sulfonate and acrylic acid, acrylic acid-vinyl acetate copolymers, and acrylic acid / sulfonic acid monomer copolymers. In this specification, (meth)acrylic acid is meant to refer collectively to acrylic acid and methacrylic acid.

[0070] (Naturally Derived Polymers) In some embodiments, naturally derived polymers are used as the water-soluble polymer. Examples of naturally derived polymers include cellulose derivatives and starch derivatives. Naturally derived polymers may be used singly or in combination of two or more. In some 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 cellulose derivatives include hydroxyethyl cellulose (HEC), hydroxypropyl cellulose, hydroxyethyl methyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, ethyl cellulose, ethyl hydroxyethyl cellulose, and carboxymethyl cellulose. Of these, HEC is preferred. One type of cellulose derivative may be used singly, or two or more types may be used in combination. In some embodiments, a starch derivative is used as the water-soluble polymer. Starch derivatives are polymers containing α-glucose units as the main repeating unit, such as pregelatinized starch, pullulan, carboxymethyl starch, and cyclodextrin. One type of starch derivative may be used singly, or two or more types may be used in combination.

[0071] In the technology disclosed herein, synthetic polymers can be preferably used as the water-soluble polymer from the viewpoint of ease of control of chemical structure and purity. In some embodiments, the polishing composition can 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.

[0072] In some aspects of the technology disclosed herein, a nonionic polymer can be preferably used as the water-soluble polymer from the viewpoints of efficient action on the silicon wafer and prevention of abrasive particle aggregation. By using a nonionic polymer as the water-soluble polymer to be used in combination with an anionic surfactant, the effect of uniformly and appropriately protecting the silicon material surface other than the LM periphery can be suitably exerted together with the anionic surfactant without inhibiting the effect of using the anionic surfactant (e.g., the effect of improving the dispersibility of abrasive particles).

[0073] (Weight-average molecular weight of water-soluble polymer) 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 may be less than or equal to 150×10 ４ The following is suitable, preferably 100 x 10 ４ or less, more preferably 80×10 ４ is less than or equal to 60×10 ４ It may be 50×10 or less. ４ It may be 25×10 or less. ４ It may be 20 × 10 or less. ４ Below, 15 x 10 ４ Less than or equal to 10 x 10 ４ It may be that the Mw of the water-soluble polymer is not too large, which can be advantageous from the viewpoint of efficiently forming a homogeneous film when used in combination with an anionic surfactant. In some preferred embodiments, the Mw of the water-soluble polymer is, for example, 8 × 10 ４ is less than or equal to 6×10 ４ It may be 4×10 or less. ４ It may be 3×10 or less. ４ or less or 2 x 10 ４ In addition, from the viewpoint of protecting the surface of the silicon material other than the periphery of the LM, the Mw of the water-soluble polymer may be 0.5 × 10 or less. ４ It is appropriate that the value is 0.8×10 or more. ４ It is preferable that the ratio is 1.0×10 or more. ４ More preferably, it is 1.5×10 or more. ４In some embodiments, the Mw of the water-soluble polymer may be 3×10 or more. ４ It may be 5×10 or more. ４ or more, 7 × 10 ４ It may be 10×10 or more. ４ That's it, 20 x 10 ４ or more or 30 x 10 ４ It may be more than that.

[0074] The Mw of the water-soluble polymer can be the molecular weight calculated from the value based on aqueous gel permeation chromatography (GPC) (aqueous, polyethylene oxide equivalent). A Tosoh Corporation model "HLC-8320GPC" can be used as the GPC measurement device. 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 wt % Column: TSKgel GMPWXL Detector: differential refractometer Eluent: 100 mM aqueous sodium nitrate solution / acetonitrile = 10-8 / 0-2 Flow rate: 1 mL / min Measurement temperature: 40°C Sample injection volume: 100 μL

[0075] Although not particularly limited, the content of the water-soluble polymer relative to the total weight of the polishing composition (when two or more water-soluble polymers are contained, the total content thereof) is, for example, 1.0 × 10 －７ % by weight or more, and from the viewpoint of protecting the surface of the silicon material, it is preferably 1.0 × 10 －６ % by weight or more, more preferably 5.0 × 10 －６ % by weight or more, and －５ % by weight or more, and －５ % by weight or more, and may be 1.0 x 10 －４ % by weight or more, and －４% or more by weight. The content of the water-soluble polymer may be, for example, 0.5% by weight or less, and from the viewpoint of maintaining the polishing rate, it is appropriate to set it to 0.1% by weight or less, preferably 0.01% by weight or less, more preferably 0.005% by weight or less, and may be 0.001% by weight or less, or may be 0.0005% by weight or less. These contents can be preferably applied, for example, to the content of the water-soluble polymer in the polishing liquid (working slurry) supplied to the object to be polished.

[0076] In the case of a polishing composition (i.e., a concentrated solution) that is diluted before use in polishing, the content of the water-soluble polymer (when two or more water-soluble polymers are contained, the total content thereof) is, for example, 1.0 × 10 －６ % by weight or more, and －５ It is appropriate to set the content to 1.0 × 10 －４ % by weight or more, and may be 1.0 x 10 －３ % by weight or more, and －３ From the viewpoints of storage stability, filterability, and the like, the total amount of the water-soluble polymer can be, for example, 5% by weight or less, suitably 1% by weight or less, preferably 0.5% by weight or less, or may be 0.1% by weight or less, or may be 0.05% by weight or less.

[0077] Abrasive grain content C in polishing composition Ａ Content C of water-soluble polymer relative to Ｐ (When two or more water-soluble polymers are contained, the total content thereof) weight ratio (C Ｐ / C Ａ ) is not particularly limited as long as the effects of the technology disclosed herein are exhibited. Ｐ / C Ａ ) is, for example, 1.0 × 10 －７ or more, and －６ In some preferred embodiments, the ratio (C Ｐ / C Ａ ) is, for example, 1.0 × 10 －５ or more, 5.0 × 10 －５ or more, and may be 1.0 × 10－４ or more, 2.0 × 10 －４ The above ratio (C Ｐ / C Ａ From the viewpoint of maintaining the polishing rate, the ratio (C Ｐ / C Ａ ) is, for example, 0.01 or less, may be 0.001 or less, or may be 0.0005 or less.

[0078] <Anionic Surfactant> The polishing composition disclosed herein further contains an anionic surfactant in addition to the abrasive grains, basic compound, and water-soluble polymer described above. Here, the anionic surfactant refers to a compound having a functional group and a hydrophobic group that dissociates into an anion in water and has surface activity. A polishing composition containing a water-soluble polymer in combination with an anionic surfactant can effectively eliminate the protrusion of the LM periphery while maintaining the polishing rate. The reason for this effect is believed to be that the combined use of a water-soluble polymer with a relatively large molecular size and an anionic surfactant with a relatively small molecular size can uniformly protect the silicon material surface (silicon wafer surface) mainly other than the LM periphery, without excessive or insufficient protection, thereby effectively eliminating the protrusion of the LM periphery while maintaining the polishing rate. The above mechanism is the inventors' theory based on experimental results, and the technology disclosed herein should not be interpreted as being limited to the above mechanism.

[0079] Examples of anionic surfactants include compounds containing at least one functional group selected from the group consisting of a sulfate (salt) group, a sulfonic acid (salt) group, a phosphonic acid (salt) group, a phosphoric acid (salt) group, and a carboxylic acid (salt) group. Of these, the functional group is preferably a sulfate (salt) group, a sulfonic acid (salt) group, a phosphoric acid (salt) group, or a phosphonic acid (salt) group, and more preferably a sulfate (salt) group, a sulfonic acid (salt) group, or a phosphoric acid (salt) group.

[0080] In this specification, the term "acid (salt)" means that the group or compound in question may be in the form of an acid or a salt. Here, the sulfonic acid group is a sulfo group, and the sulfate group is -OSO ３ H, a phosphonic acid group is a phospho group, and a phosphate group is a group represented by -OPO ３ H ２ The phosphonate group and the phosphate group may be acidic groups with one remaining hydrogen atom. These groups may be in the form of a salt, and the salt is not particularly limited, but examples thereof include ammonium salts; alkali metal salts such as lithium salts, sodium salts, and potassium salts; alkaline earth metal salts such as calcium salts; and amine salts. The type of salt may be one type alone or a combination of two or more types.

[0081] Examples of anionic surfactants having a sulfate (salt) group include alkyl sulfate ester salts (e.g., ammonium lauryl sulfate), polyoxyalkylene alkyl ether sulfate ester salts (e.g., polyoxyethylene lauryl ether ammonium sulfate), polyoxyalkylene allyl ether sulfate ester salts, polyoxyalkylene allyl phenyl ether sulfate ester salts (e.g., polyoxyethylene allyl phenyl ether sulfate ester salts), polyoxyalkylene alkyl allyl phenyl ether sulfate ester salts (e.g., polyoxyethylene alkyl allyl phenyl ether sulfate ester salts), polyoxyalkylene phenyl ether sulfate ester salts (e.g., polyoxyethylene phenyl ether sulfate ester salts), polyoxyalkylene polycyclic phenyl ether sulfate ester salts, etc. Examples of salts of sulfate groups include ammonium salts; alkali metal salts such as lithium salts, sodium salts, and potassium salts; alkaline earth metal salts such as calcium salts; amine salts; etc. These can be used alone or in appropriate combinations of two or more.

[0082] Examples of anionic surfactants having a sulfonic acid (salt) group include alkylbenzenesulfonic acids (e.g., n-dodecylbenzenesulfonic acid), alkylsulfonic acids (e.g., laurylsulfonic acid), alkyldiphenyletherdisulfonic acids (e.g., lauryldiphenyletherdisulfonic acid), alkylnaphthalenesulfonic acids (e.g., laurylnaphthalenesulfonic acid), alkylsulfosuccinic acids, polyoxyethylenesulfosuccinic acid, and salts of any of the above-mentioned compounds. Examples of salts of sulfonate groups are the same as the examples of salts of sulfate groups described above. These can be used alone or in appropriate combinations of two or more.

[0083] Examples of anionic surfactants having a phosphate (salt) group include monoalkyl phosphate, alkyl ether phosphate, polyoxyethylene alkyl ether phosphate, polyoxyethylene allyl phenyl ether phosphate, and polyoxyethylene alkyl phenyl ether phosphate. Examples of anionic surfactants having a phosphonic acid (salt) group include dodecylphosphonic acid. Examples of salts of phosphate or phosphonate groups are the same as the examples of salts of sulfate groups described above. These can be used alone or in appropriate combinations of two or more.

[0084] Examples of anionic surfactants having a carboxylic acid (salt) group include myristic acid, palmitic acid, stearic acid, lauric acid, polyoxyethylene alkyl ether acetic acid, etc. Examples of salts of carboxylic acid (salt) groups are the same as the examples of salts of sulfate groups described above. These can be used alone or in appropriate combinations of two or more. Anionic surfactants having a sulfate (salt) group can be preferably used as the anionic surfactant in the technology disclosed herein.

[0085] The molecular weight of the anionic surfactant used in the technology disclosed herein may be, for example, less than 5000, or may be 3000 or less. In order to facilitate the formation of a more uniform film in the proper amount when used in combination with a water-soluble polymer, in some embodiments, the molecular weight of the anionic surfactant is suitably 2000 or less, preferably 1000 or less, more preferably 700 or less, and may be 500 or less, 400 or less, or 350 or less (e.g., 300 or less). The molecular weight of the anionic surfactant may be the molecular weight calculated from the chemical formula, or the weight-average molecular weight value (aqueous, polyethylene glycol equivalent) determined by GPC may be used. The GPC measurement conditions can be the same as those for the water-soluble polymer described above.

[0086] Molecular weight M of anionic surfactant Ｓ Weight average molecular weight M of water-soluble polymer Ｐ The ratio (M Ｐ / M Ｓ ) is not particularly limited, and may be, for example, 2 or more, 5 or more, or 8 or more. In some embodiments, in the case of using a combination of a water-soluble polymer and an anionic surfactant, the above ratio (M Ｐ / M Ｓ ) is suitably 10 or more, advantageously 15 or more, preferably 20 or more, more preferably 25 or more, and may be 30 or more, 35 or more, 40 or more, 45 or more, or 50 or more. Ｐ / M Ｓ ) may be, for example, 500 or less, 400 or less, or 300 or less. In some embodiments, from the viewpoint of easily achieving a good balance between the effect of improving the dispersibility of abrasive grains and the effect of adequately protecting the silicon material surface other than the LM periphery, the above ratio (M Ｐ / M Ｓ) is suitably 250 or less, preferably 200 or less, may be 150 or less, may be 100 or less, or may be 80 or less.

[0087] The content of the anionic surfactant relative to the total weight of the polishing composition (when two or more kinds of anionic surfactants are contained, the total content thereof) is not particularly limited and can be appropriately set so as to obtain the desired effect of use. In some embodiments, the content of the anionic surfactant relative to the total weight of the polishing composition is, for example, 1.0 × 10 －８ % by weight or more, and from the viewpoint of protecting the surface of the silicon material, it is preferably 1.0 × 10 －７ % by weight or more, more preferably 5.0 × 10 －７ % by weight or more, and －６ % by weight or more, and －６ % by weight or more, and may be 1.0 x 10 －５ % by weight or more, and －５ The content of the anionic surfactant may be, for example, 0.05% by weight or less, and from the viewpoint of maintaining the polishing rate, it is appropriate to set it to 0.01% by weight or less, and advantageously to set it to 0.001% by weight or less, and it is preferable to set it to 5×10 －４ % by weight or less, and －４ % by weight or less, more preferably 8×10 －５ % by weight or less, and －５ % by weight or less. These contents are preferably applied to the content of the anionic surfactant in the polishing liquid (working slurry) supplied to the object to be polished, for example.

[0088] In the case of a polishing composition (i.e., a concentrated solution) that is diluted and used for polishing, the content of the anionic surfactant (when two or more kinds of anionic surfactants are contained, the total content thereof) is, for example, 1.0 × 10 －７ % by weight or more, preferably 1.0 x 10 －６ % by weight or more, more preferably 5.0 × 10 －６ % by weight or more, and －５% by weight or more, and －５ % by weight or more, and may be 1.0 x 10 －４ % by weight or more, and －４ The content of the anionic surfactant may be, for example, 0.5% by weight or less, suitably 0.1% by weight or less, advantageously 0.01% by weight or less, preferably 0.005% by weight or less, more preferably 0.001% by weight or less, and more preferably 8×10 －４ % by weight or less, and －４ It may be % by weight or less.

[0089] Abrasive grain content C in polishing composition Ａ Content C of anionic surfactant relative to Ｓ Weight ratio (C Ｓ / C Ａ ) is not particularly limited as long as the effects of the technology disclosed herein are exhibited. Ｓ / C Ａ ) is, for example, 1.0 × 10 －８ or more, and －７ In some preferred embodiments, the ratio (C Ｓ / C Ａ ) is, for example, 1.0 × 10 －６ or more, 5.0 × 10 －６ or more, and may be 1.0 × 10 －５ or more, 2.0 × 10 －５ The above ratio (C Ｓ / C Ａ From the viewpoint of maintaining the polishing rate, the ratio (C Ｓ / C Ａ ) is, for example, 0.001 or less, and 1 × 10 －４ It may be 7×10 or less. －５ Less than 5 x 10 －５ The following is also acceptable.

[0090] In the art disclosed herein, the content C of the water-soluble polymer in the polishing compositionＰ The content C of the anionic surfactant relative to Ｓ Weight ratio (C Ｓ / C Ｐ ) is not particularly limited. Ｓ / C Ｐ ) may be, for example, 10 or less, 8 or less, 5 or less, or 2 or less (for example, less than 2). In some embodiments, from the viewpoint of easily suppressing a decrease in the polishing rate, the ratio (C Ｓ / C Ｐ ) is preferably 1 or less (for example, less than 1), more preferably 0.5 or less, and even more preferably 0.3 or less. Ｓ / C Ｐ ) is suitably 0.01 or more, may be 0.05 or more, or may be 0.1 or more, from the viewpoint of making it easier to appropriately exhibit the effects of the combined use of the water-soluble polymer and the anionic surfactant.

[0091] <Water> The polishing composition disclosed herein typically 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 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. The polishing composition disclosed herein may further contain an organic solvent (e.g., a lower alcohol or a lower ketone) that is uniformly miscible with water, as needed. Generally, it is preferable that 90% by volume or more of the solvent contained in the polishing composition be water, and more preferably 95% by volume or more (e.g., 99 to 100% by volume) be water.

[0092] <Chelating Agent> In some preferred embodiments, the polishing composition disclosed herein contains a chelating agent. By including a chelating agent in the polishing composition, metal contamination of the polished surface after pre-polishing can be suppressed. One type of chelating agent may be used alone, or two or more types may be used in combination.

[0093] Examples of the chelating agent include aminocarboxylic acid chelating agents and organic phosphonic acid chelating agents. Examples of the aminocarboxylic acid chelating agent include alanine, glycine, 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, phosphonobutanetricarboxylic acid (PBTC), nitrilotris(methylenephosphonic acid) (NTMP), and α-methylphosphonosuccinic acid. Particularly preferred chelating agents include triethylenetetraminehexaacetic acid, diethylenetriaminepentaacetic acid, ethylenediaminetetrakis(methylenephosphonic acid) and diethylenetriaminepenta(methylenephosphonic acid).

[0094] The content of the chelating agent relative to the total weight of the polishing composition is, for example, 1.0 × 10 －５ In some preferred embodiments, the amount is 1.0×10 －４ % by weight or more, and －４ % by weight or more, and may be 1.0 x 10 －３The content of the chelating agent can be, for example, 0.5% by weight or less, suitably 0.1% by weight or less, and in some preferred embodiments, may be 0.01% by weight or less, or may be 0.005% by weight or less.

[0095] <Other Components> In addition to the various components described above, the polishing composition disclosed herein may further contain, as necessary, known additives that can be used in polishing compositions used in polishing steps of silicon wafers, such as inorganic acid salts, organic acid salts, preservatives, and fungicides, within the range that does not significantly impair the effects of the present invention.

[0096] For example, inorganic acid salts include salts of hydrohalic acids (e.g., hydrochloric acid, hydrobromic acid, hydroiodic acid, hydrofluoric acid), nitric acid, sulfuric acid, sulfurous acid, hydrogen sulfite, thiosulfuric acid, silicic acid, boric acid, phosphoric acid, etc. Furthermore, organic acid salts include salts of carboxylic acids (e.g., formic acid, acetic acid, propionic acid, butyric acid, citric acid, tartaric acid, trifluoroacetic acid), organic sulfonic acids (e.g., methanesulfonic acid, trifluoromethanesulfonic acid), sulfamic acid, organic phosphoric acids (e.g., ethyl phosphate), etc. The cations constituting the inorganic acid salts and organic acid salts are not particularly limited, and examples thereof include alkali metals (lithium, sodium, potassium, etc.), alkaline earth metals (calcium, strontium, barium, etc.), magnesium, ammonium, etc. For example, specific examples of sulfuric acid salts (sulfates) include lithium sulfate, sodium sulfate, potassium sulfate, ammonium sulfate, etc. It should be noted that, in this specification, the inorganic acid salts and organic acid salts used as additives do not include the basic compounds. In this specification, the organic acid salts as the additives do not include the chelating agents and the anionic surfactants.

[0097] Examples of the antiseptic and antifungal agent include isothiazolinone compounds, paraoxybenzoic acid esters, phenoxyethanol, and the like.

[0098] The polishing composition disclosed herein may contain a surfactant other than an anionic surfactant (e.g., a nonionic, cationic, or amphoteric surfactant) as needed. From the viewpoint of avoiding the inhibition of the effect of the anionic surfactant, the non-anionic surfactant is preferably a nonionic surfactant. In a polishing composition containing a surfactant other than an anionic surfactant in addition to an anionic surfactant, the content of the surfactant other than anionic surfactant is preferably 1 / 2 or less, more preferably 1 / 5 or less, and even more preferably 1 / 10 or less, of the content of the anionic surfactant, on a weight basis, from the viewpoint of favorably exhibiting the effects of the technology disclosed herein. The technology disclosed herein can be preferably implemented in an embodiment that does not contain a surfactant other than an anionic surfactant.

[0099] The polishing composition disclosed herein preferably contains substantially no oxidizing agent. If an oxidizing agent is contained in the polishing composition, the supply of the composition may oxidize the substrate surface (e.g., the surface of a silicon wafer) and form an oxide film, which may result in a decrease in the polishing rate. Here, "substantially no oxidizing agent" in a polishing composition means that an oxidizing agent is not intentionally added, and it is acceptable for a trace amount of oxidizing agent to be unavoidably present due to raw materials, manufacturing method, etc. The term "trace amount" refers to a molar concentration of the oxidizing agent in the polishing composition of 0.001 mol / L or less (preferably 0.0005 mol / L or less, more preferably 0.0001 mol / L or less, even more preferably 0.00005 mol / L or less, and particularly preferably 0.00001 mol / L or less). In some preferred embodiments, the polishing composition does not contain an oxidizing agent. The polishing composition disclosed herein can be preferably implemented in an embodiment that does not contain, for example, hydrogen peroxide, sodium persulfate, ammonium persulfate, or sodium dichloroisocyanurate.

[0100] <Polishing Composition> The polishing composition disclosed herein is supplied to an object to be polished in the form of a polishing liquid (working slurry) containing the polishing composition, for example, and used to polish the object to be polished. The polishing liquid may be prepared, for example, by diluting (e.g., with water) a concentrated solution of any of the polishing compositions disclosed herein. Alternatively, the polishing composition may be used as is as a polishing liquid. The concentration ratio of the concentrated solution may be, for example, about 2 to 140 times on a volume basis, and is usually about 5 to 80 times.

[0101] The pH of the polishing composition is, for example, 8.0 or more, preferably 8.5 or more, more preferably 9.0 or more, even more preferably 9.5 or more, and may be 10.0 or more (for example, 10.5 or more). As the pH increases, the polishing rate tends to improve. On the other hand, from the viewpoint of preventing dissolution of abrasive grains (for example, silica particles) and suppressing a decrease in the mechanical polishing action of the abrasive grains, the pH of the polishing composition is usually suitably 12.0 or less, preferably 11.8 or less, and more preferably 11.5 or less. These pH values ​​can be preferably applied to both the polishing liquid (working slurry) supplied to the object to be polished and the pH of its concentrate.

[0102] The pH of the polishing composition can be determined by using a pH meter (e.g., a glass electrode hydrogen ion concentration indicator (model number F-23) 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 polishing composition and measuring the value after stabilization for at least two minutes.

[0103] 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 polishing liquid is prepared by mixing at least Part A containing abrasive grains with Part B containing the remaining components, and diluting the mixture at an appropriate time as needed.

[0104] 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 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.

[0105] <Polishing> The polishing composition disclosed herein can be used to polish an object to be polished, for example, in an embodiment including the following steps. That is, a working slurry containing any of the polishing compositions disclosed herein is prepared. Next, the polishing composition is supplied to the object to be polished, and polished by a conventional method. For example, the object to be polished is placed in a general polishing device, and the polishing composition is supplied to the surface of the object to be polished (surface to be polished) through the polishing pad of the polishing device. For example, while continuously supplying the polishing composition, 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). Through this polishing process, polishing of the object to be polished is completed.

[0106] The polishing pad used in the polishing step is not particularly limited. For example, any of foamed polyurethane type, nonwoven fabric type, suede type, abrasive grain containing type, and abrasive grain non-containing type may be used. In addition, the polishing device may be a double-sided polishing device that polishes both sides of the object to be polished simultaneously, or a single-sided polishing device that polishes only one side of the object to be polished.

[0107] The polishing composition may be used in a manner that it is disposable after being used for polishing once (so-called "flow-through"), or may be recycled and used repeatedly. An example of a method for recycling a polishing composition is a method in which the used polishing composition discharged from a polishing machine is collected in a tank, and the collected polishing composition is supplied to the polishing machine again.

[0108] <Applications> The polishing composition disclosed herein is used for polishing silicon wafers bearing laser marks (LMs). The polishing composition can effectively eliminate the protrusions around the LMs while suppressing a decrease in the removal rate during polishing of silicon wafers bearing laser marks (LMs). The polishing composition disclosed herein can be particularly preferably used in a preliminary polishing step, more specifically, in the rough polishing step (primary polishing step), which is the first polishing step in a polishing process, and in the subsequent intermediate polishing step (secondary polishing step). Because a higher removal rate may be required in the preliminary polishing step, it is particularly useful to use the polishing composition disclosed herein in the preliminary polishing step to efficiently eliminate the protrusions around the LMs while maintaining the removal rate.

[0109] Prior to the polishing step using the polishing composition disclosed herein, the silicon wafer may be subjected to a common treatment applicable to silicon wafers, such as lapping, etching, or the application of the above-mentioned LM. The silicon wafer has, for example, a surface made of silicon. Such a silicon wafer is preferably a silicon single crystal wafer, for example, a silicon single crystal wafer obtained by slicing a silicon single crystal ingot. The polishing composition disclosed herein is suitable for use in polishing silicon single crystal wafers to which LM has been applied.

[0110] The matters disclosed in this specification include the following: [1] A polishing composition for pre-polishing a laser-marked silicon wafer, the polishing composition comprising abrasive grains, a basic compound, a water-soluble polymer, and an anionic surfactant. [2] The content C of the water-soluble polymer Ｐ The content C of the anionic surfactant relative to Ｓ Weight ratio (C Ｓ / C Ｐ) is 1 or less. [3] The polishing composition according to [1] or [2] above, which contains a nonionic water-soluble polymer as the water-soluble polymer. [4] The polishing composition according to any one of [1] to [3] above, which contains a polymer containing a nitrogen atom as the water-soluble polymer. [5] The polishing composition according to [1] above, which contains a polymer containing a nitrogen atom as the water-soluble polymer. [6] The polishing composition according to [1] above, which contains a polymer containing a nitrogen atom as the water-soluble polymer. [7] The polishing composition according to [1] above, which contains a polymer containing a nitrogen atom as the water-soluble polymer. [8] The polishing composition according to [1] above, which contains a polymer containing a nitrogen atom as the water-soluble polymer. [9] The polishing composition according to [1] above, which contains a polymer containing a nitrogen atom as the water-soluble polymer.

[10] The polishing composition according to [1] above, which contains a polymer containing a nitrogen atom as the water-soluble polymer.

[11] The polishing composition according to

[12] above, which contains a polymer containing a nitrogen atom as the water-soluble polymer.

[12] The polishing composition according to

[13] above, which contains a polymer containing a nitrogen atom as the water-soluble polymer.

[13] The polishing composition according to

[14] above, which contains a polymer containing a nitrogen atom as the water-soluble polymer.

[14] The polishing composition according to

[15] above, which contains a polymer containing a nitrogen atom as the water-soluble polymer.

[15] The polishing composition according to

[16] above, which contains a polymer containing a nitrogen atom as the water-soluble polymer.

[16] The polishing composition according to

[17] above, which contains a polymer containing a nitrogen atom as the water-soluble polymer.

[17] The polishing composition according to

[18] above, which contains a polymer containing a nitrogen atom as the water-soluble polymer.

[18] The polishing composition according to

[19] above, which contains a polymer containing a nitrogen atom as the water-soluble polymer.

[19] The polishing composition according to ４

[0013] The polishing composition according to any one of [1] to [4] above, which contains the following water-soluble polymer: [6] The polishing composition according to any one of [1] to [5] above, which contains silica particles as the abrasive grains; [7] The polishing composition according to any one of [1] to [6] above, which further contains a chelating agent; [8] A concentrated solution of the polishing composition according to any one of [1] to [7] above; [9] A polishing method, which comprises pre-polishing a laser-marked silicon wafer with the polishing composition according to any one of [1] to [8] above.

[0111] Hereinafter, several examples of the present invention will be described, but it is not intended that the present invention be limited to those shown in these examples.

[0112] <Preparation of Polishing Composition> (Example 1) A polishing composition containing colloidal silica (average primary particle diameter: 55 nm) as abrasive grains, tetramethylammonium hydroxide (TMAH) and potassium carbonate as basic compounds, and a water-soluble polymer having a Mw of 1.7 × 10 ４A concentrated polishing composition was prepared by mixing polyvinylpyrrolidone (PVP) of 100% by weight, ammonium lauryl sulfate as an anionic surfactant, ethylenediaminetetrakis(methylenephosphonic acid) (EDTPO) as a chelating agent, and ion-exchanged water. The resulting concentrated polishing composition was diluted 30 times by volume with ion-exchanged water to obtain a polishing composition containing 10 g / L of abrasive grains, 1.1 g / L in total of basic compounds (breakdown: TMAH 0.7 g / L, potassium carbonate 0.4 g / L), PVP 0.003 g / L, ammonium lauryl sulfate 0.0003 g / L, and EDTPO 0.01 g / L. The approximate content [wt%] of each component in the polishing composition was calculated by multiplying the content [g / L] of each component in the polishing composition by 0.1. The same applies to the following examples and comparative examples.

[0113] Example 2 A polishing composition according to this example was obtained in the same manner as in Example 1, except that the content of ammonium lauryl sulfate was changed to 0.0006 g / L.

[0114] Comparative Example 1 A polishing composition according to this example was obtained in the same manner as in Example 1, except that no anionic surfactant was used.

[0115] Comparative Example 2 A polishing composition according to this example was obtained in the same manner as in Example 1, except that no water-soluble polymer was used.

[0116] Comparative Example 3 A polishing composition according to this example was obtained in the same manner as in Example 1, except that neither the water-soluble polymer nor the anionic surfactant was used.

[0117] <Performance Evaluation> (Polishing of Silicon Wafer) The polishing composition according to each example was used as a polishing liquid (working slurry) to polish the surface of a workpiece (test piece) under the following conditions. A commercially available silicon single crystal wafer (thickness: 545 μm, conductivity type: P-type, crystal orientation: <100>, resistivity: 1 Ω cm or more and less than 100 Ω cm) with a diameter of 100 mm that had been lapped and etched was used as the test piece. LM was attached to the wafer. (Polishing conditions) Polishing device: Single-sided polishing device manufactured by Engis Japan, model "EJ-380IN" Polishing pressure: 12 kPa Platen rotation speed: +50 rpm (counterclockwise rotation is positive (+); same below.) Head rotation speed: +50 rpm Polishing pad: Nitta DuPont, product name "SUBA800" Polishing liquid supply rate: 50 mL / min (flowing) Maintained temperature of polishing environment: 25°C Polishing removal rate: 4 μm

[0118] (Evaluation of Polishing Rate) During the polishing, the polishing rate R [μm / min] in each Example and Comparative Example was calculated using the following formulas (1) to (3) based on the difference in weight of the wafer before and after 10 minutes of polishing. The obtained polishing rate R was converted into a relative value (relative polishing rate [%]) with the polishing rate of Comparative Example 1 set to 100%. The obtained results are shown in the "relative polishing rate" column in Table 1. If the relative polishing rate is 95% or more, it is evaluated that the polishing rate is maintained. Formulas: ΔV=(W0-W1) / d (1) Δx=ΔV / S (2) R=Δx / t×10 ４ (3) ΔV: wafer volume change before and after polishing [cm ３ ] W0: wafer weight before polishing [g] W1: wafer weight after polishing [g] d: specific gravity of silicon (2.33) [g / cm ３ ] S: wafer surface area [cm ２ ] Δx: change in wafer thickness before and after polishing [cm] t: polishing time [min]

[0119] (Evaluation of LM Flatness) The surface shape of the LM peripheral portion of the polished silicon wafer was measured using a stylus surface roughness profiler (SURFCOM 1500DX, manufactured by Tokyo Seimitsu Co., Ltd.). Specifically, the stylus of the measuring instrument was brought into contact with the surface of the substrate and run along the LM peripheral portion to measure the portion where no protrusion occurred (reference surface) and the height of the protrusion. The height [μm] from the reference surface to the highest point of the protrusion was then taken as the LM flatness. The obtained LM flatness was converted into a relative value (relative LM flatness [%]) with the flatness of Comparative Example 1 taken as 100%. The obtained results are shown in the "Relative LM Flatness" column in Table 1. A relative LM flatness of 90% or less was evaluated as having excellent protrusion elimination ability.

[0120]

[0121] As shown in Table 1, the polishing compositions of Examples 1 and 2, which contained a combination of a water-soluble polymer and an anionic surfactant, were able to improve the ability to eliminate LM peripheral protuberances while maintaining an equivalent or higher removal rate compared to the polishing composition of Comparative Example 1, which contained a water-soluble polymer but no anionic surfactant. On the other hand, the ability to eliminate LM peripheral protuberances of the polishing composition of Comparative Example 2, which used an anionic surfactant alone, was higher than that of Comparative Example 3, which contained neither a water-soluble polymer nor an anionic surfactant, but was significantly lower than that of Examples 1 and 2 and did not even reach Comparative Example 1.

[0122] 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 pre-polishing a laser-marked silicon wafer, comprising abrasive grains, a basic compound, a water-soluble polymer, and an anionic surfactant.

2. Content C of the water-soluble polymer Ｐ The content C of the anionic surfactant relative to Ｓ Weight ratio (C Ｓ / C Ｐ 2. The polishing composition according to claim 1, wherein the value of (a) is 1 or less.

3. The polishing composition according to claim 1 or 2, wherein the water-soluble polymer comprises a nonionic water-soluble polymer.

4. The polishing composition according to claim 1 or 2, wherein the water-soluble polymer comprises a polymer containing a nitrogen atom.

5. The water-soluble polymer has a weight average molecular weight of 80 x 10 ４ The polishing composition according to claim 1 or 2, comprising the following water-soluble polymer:

6. The polishing composition according to claim 1 or 2, wherein the abrasive grains comprise silica particles.

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

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

9. A polishing method comprising pre-polishing a laser-marked silicon wafer with the polishing composition according to claim 1 or 2.

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